According to JuicePlotter, my HTC Evo's 3G radio is always on when the screen is on -- even when doing absolutely nothing. I tested this by turning the brightness down to 1 and opening the settings menu and just leaving it there. The screen was set to never shut off. I got pretty significant battery drain.
I ask because I want to improve my battery life when reading downloaded books with the Kindle app. It seems to me that the radio should be in sleep mode when not in use. I'd rather not switch to airplane mode because I'd still like to receive calls/texts.
- I have a strong signal at all times
- When the screen is off, JuicePlotter says the radio is off (and the battery lasts practically forever)
- When in airplane mode with the screen on, JuicePlotter says the radio is off (duh) and the battery life is much better.
- Android reports that my display only consumes between 5 and 10% of power
- Android reports that Cell Standby consumes 30% (and that's with great signal)
I think these tests demonstrate that the display itself is not the problem, the radio is. So again the question is: why does the radio use so much power when the screen is on but it's not being used?